This invention relates to improved semiconductor devices and, more particularly, to a package for high current semiconductor devices using one or more semiconductor chips.
High power semiconductor devices are widely used but nonetheless costly. Their high cost stems principally from the use of expensive materials and complicated means of assembly. For example, prior art semiconductor power devices typically utilize massive copper bases, many internal piece parts, expensive ceramic insulators, and expensive assembly techniques.
In addition to being costly, prior art power semiconductor devices of high current carrying capacity are difficult or awkward to install, particularly when they must be grouped into arrays of several devices and isolated from the mounting surface. The shape and terminal arrangements of prior art devices make it inconvenient to assemble them to heat sinks and to the bus bars which interconnect the devices in an array. For example, flexible leads are frequently provided requiring that bus bars be independently supported. Furthermore, many prior art devices do not meet the minimum terminal spacing requirements which have been established by the Underwriters Laboratories in Bulletin UL508, Table 18.1 dated Aug. 19, 1977, as the recommended practice for components which are to be utilized in industrial environments. According to these recommendations, one-half inch (1.27 cm) is to be maintained through air between a high voltage ("hot") lead and the heat sink or cabinet to which the device is mounted, and three-eighths inch (0.76 cm) through air between any other terminals of substantially different potential.
Some attempts have been made to design new power semiconductor devices which are easier to install and use, particularly in arrays. However, these improved devices have not overcome all of the deficiencies of the prior art devices and are still costly. Thus a need continues to exist for low cost, rugged semiconductor power devices which are well adapted to industrial environments, which are easy to install and use mechanically, and which permit a flexible self-supporting arrangement of interconnecting bus bars.
Accordingly, it is an object of the present invention to provide an improved semiconductor power device of lower cost for a given performance rating.
It is a further object of this invention to provide an improved semiconductor power device meeting recommended minimum spacing of hot leads.
It is an additional object of this invention to provide an improved semiconductor power device which has great flexibility of installation and mechanical convenience of use.
It is a further object of this invention to provide an improved semiconductor power device which is rugged and especially suitable for industrial environments.
It is an additional object of this invention to provide an improved semiconductor device which is assembled from a small number of piece parts held in place by a dielectric adhesive.
It is a further object of this invention to provide an improved semiconductor power device which is particularly adapted to enable the use of a plurality of semiconductor chips.
It is an additional object of this invention to provide an improved semiconductor device wherein internal electrodes or terminal members are arranged to simplify connection of a plurality of semiconductor chips to said terminal members without crossover of the interconnection means.
It is a further object of the present invention to provide an improved method for the manufacture of semiconductor power devices of improved performance.
It is an additional object of the present invention to provide high current power terminals which directly support bus bars in a plane separated from the plane of the control or signal leads.